Electroplating barrel

ABSTRACT

The invention relates to an electroplating barrel whose barrel shell consists of a plurality of plastic shell elements ( 11 ) which are firmly interlinked across the circumference of the shell by gluing or welding without preheating. The shell elements ( 11 ) facilitate the production of polygonal barrel shells ( 10 ) of different cross-sections. To this end, the shell elements ( 11 ) have respective integrally formed rib-shaped projections ( 16  and  18 ), whose outer surfaces ( 21, 22 ) form between them an angle α. The sides of said angle intersect in the barrel axis a-a and the degree of angle is determined, for example, for a maximum number of shell elements ( 11 ) that are to be firmly interlinked. The profile of the rib-shaped projections ( 16, 18 ) is chosen in such a manner that in the present case the angle α can be increased to produce an electroplating barrel from a smaller quantity of shell elements ( 11 ) by machining the rib outer surfaces ( 21, 22 ).

BACKGROUND OF THE INVENTION

The invention concerns an electroplating barrel having a perforatedbarrel shell with a peripheral barrel opening which can be closed by alid, and with a cylindrical peripheral shape of non-circularcross-section, and being formed from a plurality of perforated plasticshell elements having a square shape when projected onto a plane,radially with respect to the barrel axis a-a, and which are eachconnected to another by one longitudinal rib at their longitudinal sidesextending parallel to the barrel axis a-a.

In electroplating barrels of this type, each longitudinal side of theplastic perforated shell elements, which form the barrel shell, iswelded to one longitudinal plastic rib, each extending in the axialdirection of the barrel. Usually, the polygonal barrel shell has ahexagonal cross-section and the longitudinal edges of the shell elementsmust be correspondingly bevelled to be welded over a large area to thelongitudinal connecting rib (see DE-OS 30 19 719 A1).

The production of such a barrel shell is therefore time-consuming sincethe longitudinal ribs must be butt welded along each of theirlongitudinal sides to one shell element using heat reflectors, requiringtwo welding processes for each longitudinal rib.

This barrel construction has the serious disadvantage that barrelvolumes of different sizes require shell elements with correspondinglydifferentiated transverse front ends.

It is therefore the underlying purpose of the present invention toprovide an electroplating barrel, which does not require the usualwelding processes for mutual connection of their shell elements, andwhich permits modification of the volume of the barrel shell to acertain degree without adjustment of the transverse front end size ofthe shell elements or with shell elements of the same width.

SUMMARY OF THE INVENTION

This object is achieved in accordance with the invention in that eachlongitudinal rib is formed by two rib-shaped projections, which areconnected to each other through gluing or cold welding, which areattached to a longitudinal side of a neighboring shell element, andwhich define an outer rib surface, wherein the outer rib surfacesubtends an angle α whose legs intersect on the barrel axis a-a andwhose angular size is defined by a number of shell elements which are tobe rigidly connected to one another, wherein the cross-section of therib-shaped projections is such that the angle α can be changedappropriately for producing an electroplating barrel having a differentnumber of shell elements through machining of the outer rib surfaces.

The longitudinal rib connecting the two neighboring shell elements ofthis barrel construction is divided into two rib-shaped projectionswhich are each formed on one of the two longitudinal sides of the shellelements. Connection of the rib-shaped projections of neighboring shellelements can therefore be realized in one single working step throughgluing or so-called cold welding (application of a solvent fordissolving the plastic material), wherein conventional bevelling of thelongitudinal edges of the shell elements in connection with alongitudinal rib can be completely omitted.

The cross-section of the rib-shaped projections is thereby selected suchthat the barrel shells can be produced with different cross-sections orcross-sectional shapes. The cross-section of the rib-shaped projectionsor of the angles defined by the outer surfaces of these ribs is selectedsuch that lateral joining of shell elements produces a desired barrelshell size, as defined by e.g. seven shell elements.

If barrel shells are to be produced having a smaller number of shellelements or with correspondingly smaller volume, only the outer surfaceof the rib-shaped projections must be changed e.g. by milling, tocorrespondingly increase the angle which they define.

The invention therefore permits mutual orientation of shell elements ofidentical cross-section at different angle settings to permit productionof barrel shells of different cross-sectional shapes from identicallyformed shell elements, wherein the initial shape of the shell elementsmay be such that machining of the rib-shaped projections permitsassembly of barrel shells with a smaller or larger number of shellelements.

In a preferred embodiment of the insertion, the rib-shaped projectionsform longitudinal ribs projecting outwardly from the barrel shell whichare interconnected across an entire rib height. This has the advantagethat they can be clamped together, using a clamping device, for mutualconnection using a glue or a solvent for softening the outer surface ofthe ribs to achieve a homogeneous mutual connection.

Advantageously, the outer surfaces of the ribs of each shell element ofa barrel shell design in accordance with the invention subtend an angleof approximately 60° which converges in the direction of the barrelinterior. This is advantageous for applying a clamping tool to clampneighboring rib-shaped projections.

To avoid indentations in the outer surfaces of the ribs of the shellelements produced during injection molding, provision of a channel inthe rib-shaped projections is proposed which produces favorable wallthicknesses for the rib-shaped projections. In this embodiment, therib-shaped projections have a substantially rectangular cross-sectionand can be penetrated in the longitudinal direction by a channel whosecross-sectional shape matches the cross-section of the longitudinalribs. In a further development of the rib-shaped projections a sealedmetal core is inserted into the channel. This guarantees that thesecannot yield during mutual clamping.

The perforated wall of the shell elements may be flat. In a preferreddesign, the perforated wall part of the shell elements, which isdisposed between the rib-shaped projections, is outwardly curved aboutan axis which is parallel to the barrel axis a-a. The outwardly curvedwall is advantageous in that the barrel content optimally passes closelyby the anode of the electroplating bath during rotation of the barrel.In addition, flat parts which are to be electroplated are therebyprevented from sticking to the inside wall of the shell elements.

The convex wall curvature in connection with the rib-shaped projectionsformed on the side of the shell elements produces rib-like elevations onthe inner circumference of the barrel along each shell line to ensuregood material circulation.

In one shell element design, transverse braces are formed on the outsideof the shell elements, which bridge the separation between therib-shaped projections of the shell elements. Each front end of theshell elements can be flush with one of the transverse braces. This isadvantageous in that the perforated wall can be produced withappropriately small thickness and less material thereby providingsufficient stability.

The thickness of the transverse braces is advantageously selected suchthat the shell elements can be separated along a transverse center of abrace. Joining and homogeneous connection of the front ends of the shellelements, and optionally of an appropriately shortened shell element, inthe direction of the barrel axis permits production of barrels ofdesired, stepped lengths, wherein shell elements of identical format canalways be used together with only one, appropriately shortened, shellelement.

The maximum length of the shell elements will thereby advantageously beselected such that their length can accommodate the smallest barrellength of a barrel production program.

The perforation of the shell elements is advantageously in the form of aslit, wherein the slits are preferably placed at separations from oneanother. A slitted perforation of this type has a particularly favorableeffect on the electron flow during electroplating when the slits extendin the circumferential direction of the barrel.

In accordance with a preferred embodiment of the invention, the shellelements are formed in one piece from polymer (PUR). The perforated wallpart of the shell elements can be formed from polymer (PUR) and theirlateral rib-shaped projections from another thermoplastic material.Either the complete shell elements or merely their perforated wall partcan be injected from a polymer to guarantee long service life. In thelatter case, their lateral rib-shaped projections can be produced from aless expensive thermoplastic material, preferably polypropylene orpolyethylene. The cross-section of the wall part and rib-shapedprojections must then be such that the rib-shaped projections can beinjected with the wall part in a form-locking fashion. Combination ofdifferent thermoplastic materials, such as e.g. polymer (PUR) andpolyethylene for rib-shaped projections and perforated wall parts of theshell elements is generally regarded as advantageous for electroplatingbarrels.

The combination of the above-mentioned plastic materials has thefollowing advantage:

Electroplating barrels are usually produced from only one single plasticmaterial, i.e. polypropylene or polyethylene. This has the disadvantagethat the perforations in the barrel shell narrow or become largelyblocked after a period of time due to the presence of small particles orobjects circulating in the barrel, which often have sharp edges. Thepresent combination of plastic materials eliminates this severedisadvantage of the electroplating process.

In a further embodiment of the invention, the plastic barrel front wallsare formed of sector-shaped front wall parts which are sidewardlyconnected to one another through gluing or cold-welding and formtogether a central bearing hub. This permits advantageous production ofrelatively large barrel front wall surfaces using a relatively smallinjection mold, which can be produced at low cost. Formation of thesector-shaped front wall from a number of sector-shaped front wall partswhich corresponds to the number of shell elements, is advantageous inthat each of their lateral rib-shaped projections can be made tocoincide with one front surface of the longitudinal ribs of the barrelshell formed by the lateral rib-shaped projections and connectingthereto when gluing or cold welding each barrel front wall to a frontend of the barrel shell.

In a preferred construction of the front wall parts, the sides of thefront wall parts have an integrally formed rib-shaped projection, andneighboring rib-shaped projections are glued or cold-welded to form alongitudinal rib, wherein the longitudinal ribs project radiallyoutwardly beyond the front wall parts at the barrel periphery and coverlongitudinal ribs formed by the rib-shaped projections of the shellelements at the front end of the barrel. Analog to the shell elements,the rib-shaped projections can be formed of the same plastic material orof a different thermoplastic material than the front wall parts.

The proposed design of the barrel front walls is particularlyadvantageous when they are perforated over at least a portion of theirwall surface. In this case, the injection tool must only be providedwith corresponding projections for forming perforations throughout arelatively small surface region.

BRIEF DESCRIPTION OF THE DRAWING

The drawing shows embodiments of the invention.

FIG. 1 shows a side view of an electroplating barrel;

FIG. 2 shows an end view of the electroplating barrel according to FIG.1;

FIG. 3 shows a top view onto a shell element of the electroplatingbarrel;

FIG. 4 shows a cross-section through the shell element along line IV—IVof FIG. 3;

FIG. 5 shows a cross-section through a barrel shell having a firstvolume and assembled from shell elements of identical size;

FIG. 6 shows a cross-section through a barrel shell having a secondvolume and assembled from shell elements having the same size as thoseof FIG. 5;

FIG. 7 shows a cross-section through a barrel shell having a thirdvolume and assembled from shell elements having the same size as thoseof FIGS. 5 and 6.

FIG. 8 shows a sector-shaped front wall part for forming the barrelfront walls;

FIG. 9 shows a section through the front wall part along line IX—IX ofFIG. 8.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The electroplating barrel according to FIGS. 1 and 2 comprises a barrelshell 10 which is formed e.g. of a plurality of shell elements 11 madefrom plastic material, in particular polymer (PUR) and which areinterconnected at their longitudinal and front ends through gluing orcold welding. One of such elements is shown in the top view of FIG. 3.

The periphery of the barrel shell 10 is conventionally provided with alid which can be removed from the barrel for introducing and removingmaterial to be electroplated.

Each front end of the barrel shell 10 is closed by one respective barrelfront end 12 and 14 which are also glued or cold-welded thereto and eachof which having one barrel bearing hub 12′ and 14′, respectively. Theconstruction of these barrel front walls 12,14 is described in detailbelow. The barrel front walls can also be produced as a molded body, inone piece.

The shell elements 11 have a rectangular shape when projected onto aplane, radially with respect to the barrel axis a-a. The twolongitudinal sides thereof, which extend parallel to the barrel axisa-a, are each provided with a rib-shaped projection 16 and 18 whichproject outwardly from the shell element 11 in a bar-like manner (FIG.3).

The length of the shell elements 11 can correspond to the total lengthof a barrel shell. Their length preferably corresponds to a minimumbarrel length such that for one desired barrel length, several suchshell elements 11 can be joined at their front walls (see FIG. 1).

In this case, the individual shell elements 11 have an axial length bwhich would permit production of a polygonal barrel shell 10 of aminimum length b from shell elements 11 rigidly connected to one anotherin the circumferential direction of the barrel.

The barrel shell 10 can comprise flat perforated shell wall parts 20. Inthe present case, these are preferably convexly curved toward theoutside about an axis which is parallel to the barrel axis a-a (FIG. 5).

The cross-section of the rib-shaped projections 16,18 is selected toproduce polygonal barrel shells of different barrel cross-sectionalsizes or different numbers of shell elements 11.

Towards this end, the cross-section of the rib-shaped projections 16,18is hereby selected such that corresponding finishing of the flat outersurfaces 21 and 22 of the ribs, based on a maximum possible number ofe.g. seven shell elements 11 (FIG. 7), permits production of barrelshells having e.g. only 5 or 6 shell elements 11 (FIGS. 5 and 6),wherein all these barrel shells require only one single injection moldfor one single shell element 11.

In the present embodiment, the rib-shaped projections 16,18 have arectangular cross-section and project outwardly beyond the barrelcircumference. The projecting part of the rib-shaped projections 16,18thereby serves for applying a clamping tool for clamping the outer ribsurfaces 21,22 of the rib-shaped projections 16,18 to be rigidlyconnected e.g. by gluing.

In the finished injected state, the two flat outer rib surfaces 21,22define an angle α, whose legs intersect on the barrel axis, of e.g. 55°for producing a barrel shell from a total of seven shell elements 11. Ifthe number of the shell elements 11 should be reduced as e.g. explainedabove, the angle α must be correspondingly increased through machining,e.g. milling, of the outer rib surfaces 21,22, for e.g. five shellelements 11 to 75°, and for e.g. six shell elements 11 to 65°.

The angle α can also be selected such that subsequent reduction thereofpermits production of barrel shells with a correspondingly larger numberof shell elements.

FIG. 4 shows that one channel 23 passes through each rib-shapedprojection 16,18 in the longitudinal direction, into which a sealed coreis inserted made e.g. of flat iron 24. This measure prevents so-calledindentations on the outer rib surfaces 21,22 during injection of theshell elements 11 and simultaneously provides transverse reinforcementof the rib-shaped projections 16,18 for clamping neighboring rib-shapedprojections 16,18 to be glued or cold-welded together.

This figure also shows that the flat inner surfaces 28 and 30 of therib-shaped projections 16,18 are inclined toward the inside, preferablyat an angle β of approximately 12°. This cross-sectional shape of therib-shaped projections 16,18 is favorable for receiving the clampingdevice.

To save material for the production of the convexly curved shell wallpart 20, i.e. make the wall correspondingly thin, e.g. five transversebraces 36 are formed on the outside thereof and are disposed atidentical separations, parallel to each other, and which bridge theseparation between the two rib-shaped projections 16,18. The two outerbraces 36 are flush with the front end of the shell elements 11.

This permits abutment and gluing together of several shell elements 11to obtain a desired barrel length. The shell wall part 20 is preferablyperforated by slits displaced at separations from each other whichextend in the circumferential direction of the barrel.

When the rib-shaped projections 16,18 of the shell elements 11, whichare glued or cold-welded to one another, are shaped in a sufficientlyinward manner, they form longitudinal ribs on the inner circumference ofthe barrel which promote circulation of the material to beelectroplated. The cross-sectional shape of the shell elements 11 alsopermits advantageous arrangement of the barrel lid by engagement thereofand corresponding fastening between two shell elements in anautomatically adjusting fashion, analog to the mutual arrangement of theshell elements 11. In a preferred construction variant of the shellelements 11, only their shell wall part 20 is injected from polymer(PUR) and their lateral rib-shaped projections 16,18 are injected from aconventional thermoplastic material, e.g. polypropylene (PP) orpolyethylene, to reduce costs. In this case, one of the parts 16,20 and18,20 to be connected is preferably provided with undercut longitudinalgrooves to obtain a form-locking mutual connection of these parts duringthe injection process.

The barrel front walls 12,14 can be produced from a plurality ofidentical sector-shaped front wall parts 39 which are laterally glued orcold-welded (FIGS. 8 and 9) and which each bear a sector-shaped part 39′of the bearing hub 12′ and 14′. Rib-shaped projections 40,42, which aresuitably provided with a core, are formed on their sides, each having aflat outer surface 40′ or 42′ with which they can be glued orcold-welded to an outer surface of a rib-shaped projection 40 and 42 ofa neighboring front wall part 39.

When mounting the barrel front walls 12,14 to the front walls of thebarrel shell 10, the radially outwardly projecting end pieces 40″ and42″ of the radial ribs of the barrel front walls 12,14 formed byinterconnected rib-shaped projections 40,42 thereby cover the front endsof the longitudinal ribs 26 of the shell. 46 designates a perforatedsurface part of the front wall parts 39.

I claim:
 1. An electroplating barrel having a perforated barrel openingwhich can be closed by a lid, the barrel comprising: a perforated barrelshell having a substantially cylindrical peripheral shape ofnon-circular cross section, said shell formed from a plurality ofperforated plastic shell elements, said elements having a rectangularshape when flatted, each shell element having a first rib-shapedprojection disposed at a first edge of said shell element and a secondrib-shaped projection disposed at a second edge of said shell elementwhich is opposite to said first edge, wherein said first and secondrib-shaped projections define outer rib surfaces, with each rib-shapedprojection being glued or cold-welded to a rib-shaped projection of aneighboring shell element at said outer rib surfaces to define ribsextending substantially parallel to a longitudinal axis of the barrel,said outer rib surfaces subtending an azimuthal angle α with respect tosaid longitudinal barrel axis, said angle α having a size defined by anumber of shell elements spanning a circumference of the barrel, whereineach rib-shaped projection has a cross section which can be machined atsaid outer rib surfaces to appropriately change said angle α to producean electroplating barrel having a different number of said shellelements.
 2. The electroplating barrel of claim 1, wherein saidrib-shaped projections form longitudinal ribs projecting outwardly fromthe barrel shell which are interconnected across an entire rib height.3. The electroplating barrel of claim 1, wherein said rib-shapedprojections have a substantially rectangular cross-section and arepenetrated in a longitudinal direction by a channel whosecross-sectional shape is adjusted to a cross-section of said rib-shapedprojections.
 4. The electroplating barrel of claim 3, further comprisinga sealed metal core, inserted into said channel.
 5. The electroplatingbarrel of claim 1, wherein a perforated wall part of said shellelements, which is disposed between said rib-shaped projections, isoutwardly curved about an axis which is parallel to said barrel axis. 6.The electroplating barrel of claim 5, further comprising transversebraces formed on an outside of said shell elements which bridge aseparation between said rib-shaped projections.
 7. The electroplatingbarrel of claim 6, wherein each front end of said shell elements isflush with one of said transverse braces.
 8. The electroplating barrelof claim 1, wherein said shell elements are formed in one piece from oneof a polymer and PUR.
 9. The electroplating barrel of claim 1, wherein aperforated wall part of said shell elements is formed from one of apolymer and PUR and said rib-shaped projections are formed from anotherthermoplastic material.
 10. The electroplating barrel of claim 1,wherein said rib-shaped projections are made from polyethylene.
 11. Theelectroplating barrel of claim 1, wherein said rib-shaped projectionsare made from polypropylene (PP).
 12. The electroplating barrel of claim1, further comprising plastic barrel front walls formed of sector-shapedfront wall parts which are sidewardly connected to one another throughgluing or cold-welding and form together a central bearing hub.
 13. Theelectroplating barrel of claim 12, wherein said barrel front walls areformed of a number of said sector-shaped front wall parts correspondingto a number of said shell elements.
 14. The electroplating barrel ofclaim 13, wherein said front wall parts are perforated at least overpart of their wall surface.
 15. The electroplating barrel of claim 12,wherein sides of said front wall parts have an integrally formed frontrib-shaped projection, and neighboring front rib-shaped projections areglued or cold-welded to form radial ribs, wherein said radial ribsproject radially outwardly beyond said front wall parts at a barrelperiphery and cover said ribs, formed by said rib-shaped projections ofsaid shell elements, at a front end of the barrel.